Low-temperature synthesis in the dittmarite–sodium acetate trihydrate system: electrochemical activity of M3+/M2+ redox couples in AMPO4 (A = Na, Li; M = Mn, Mn/Fe)

Abstract

Phase-pure NaMPO4 (M = Mn, Mn/Fe; isotypic to triphylite) and Li(Mn/Fe)PO4 were isolated as a result of the low- temperature reaction between NH4MPO4·H2O (M = Mn, Mn/Fe) and AcONa·3H2O or AcOLi, respectively. Electrochemical tests in half-cells revealed that Na-based compounds exhibit poor electrochemical activity vs. metallic Na, while the similarly synthesized Li counterpart demonstrates decent cycling in Na cells. The synthetic features, crystal structures and properties of related members of the olivine family are discussed.